Polymerization of Allenes by Using an Iron(II) β-Diketiminate Pre-Catalyst to Generate High Mn Polymers

Callum R Woof; Derek J Durand; Ruth L Webster

doi:10.1002/chem.202101078

Polymerization of Allenes by Using an Iron(II) β-Diketiminate Pre-Catalyst to Generate High M_n Polymers

Chemistry. 2021 Aug 25;27(48):12335-12340. doi: 10.1002/chem.202101078. Epub 2021 Jul 16.

Authors

Callum R Woof¹, Derek J Durand², Ruth L Webster¹

Affiliations

¹ Department of Chemistry, University of Bath Claverton Down, Bath, BA2 7AY, UK.
² School of Chemistry, University of Bristol Cantock's Close, Bristol, BS8 1TS, UK.

Abstract

Herein, we report an iron(II)-catalyzed polymerization of arylallenes. This reaction proceeds rapidly at room temperature in the presence of a hydride co-catalyst to generate polymers of weight up to M_n =189 000 Da. We have determined the polymer structure and chain length for a range of monomers through a combination of NMR, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC) analysis. Mechanistically, we postulate that the co-catalyst does not react to form an iron(II) hydride in situ, but instead the chain growth is proceeding via a reactive Fe(III) species. We have also performed kinetic and isotopic experiments to further our understanding. The formation of a highly unusual 1,3-substituted cyclobutane side-product is also investigated.

Keywords: allenes; cycloaddition; homogeneous catalysis; iron; polymers.

Grants and funding

Engineering and Physical Sciences Research Council